1. Field of the Invention
The present invention relates to a method of coating three dimensional and non-uniform objects with molecular sieves using pulsed laser deposition.
2. Description of Related Art
There are a variety of methods for fabricating molecular sieves into thin films. A popular approach is the seed method, which involves the deposition of colloidal suspensions of zeolite nanosols onto a flat substrate followed by a controlled secondary growth of the nanoparticles. The resulting films are generally continuous and sometimes oriented. It appears, however, that the seed method works best with only a few types of zeolites, especially those with crystal morphologies that efficiently pack on the substrate surface such as zeolite NaA or ZSM-5. This also implies that this method works best on flat surfaces. Consequently, there are relatively few examples of zeolite films and no examples of oriented films on non-planar surfaces.
The deposition-during-synthesis technique has been used to grow zeolite Beta onto macroporous alumina spheres with a 4% loading by immersing the support in the synthesis mixture. Analogously, metal and ceramic monoliths have also been coated with zeolite Beta, Mordenite, and ZSM-5 utilizing this technique. Molecular sieve films prepared by the direct deposition of crystals from solution, however, often suffer from defects and poor adhesion. Furthermore, controlling the film thickness and orientation can be quite a challenge.
In one respect, the invention is a method of coating a substrate. A target is provided. Material is ablated from the target to create a plume. The substrate is manipulated in the plume to coat the substrate with a film, and the film is heated in a synthesis gel of the target. In another respect, the invention is a coated substrate made by this method.
In other aspects, the heating of the film forms an oriented film. The oriented film may include crystals normal to the surface of the substrate. The target may include a zeolite. The zeolite may include at least one of UTD-1, ZSM-5, Beta, Mordenite, NaX, NaA, SSZ-33, SSZ-31, SSZ-42, MCM-22, or a mixture thereof. The target may include a phosphate. The phosphate may include an aluminum phosphate. The aluminum phosphate may include at least one of VPI-5, AlPO4-5, AlPO4-8, or a mixture thereof. The phosphate may include a silicon aluminum phosphate. The silicon aluminum phosphate may include at least one of SAPO-5, SAPO-37, SAPO-42, or a mixture thereof. The phosphate may include a metal aluminum phosphate. The metal aluminum phosphate may include at least one of MAPO-39, MAPO-5, MAPO-11, UCSB-6, UCSB7, or a mixture thereof. The target may include a mesoporous molecular sieve. The mesoporous molecular sieve may include at least one of MCM-41, MCM-48, SBA-15, SBA-16, Nb-TMS-1, Ti-TMS-1, Ta-TMS-1, or a mixture thereof. The ablating may include subjecting the target to pulsed radiation from an excimer laser. The laser may include a KrF* laser operating between about 70 and about 200 mJ/pulse with a repetition rate between about 1 and about 50 Hz. The manipulating may include moving the plume relative to the substrate. The manipulating may include vibrating the substrate. The heating may include heating between about 1 hour and about 200 hours. The method may also include adjusting a background pressure of the substrate to between about 150 mTorr and about 350 mTorr. The background pressure may include a background pressure of O2. The substrate may include a zeolite crystal, glass, metal, metal oxide, or plastic. The substrate may include a porous substrate. The largest dimension of the substrate may be between about 10 nm and about 10 mm. The substrate may be spherical. The method may also include washing or calcining the oriented film.
In another respect, the invention is a method of coating a substrate with an oriented film. A target including Cp*2Co+ or Cp2Fe is provided. Material is laser ablated from the target to create a plume. The substrate is vibrated in the plume to coat a film on the substrate, and the film is heated in a synthesis gel of the target to form the oriented film. In another respect, the invention is a coated substrate made by this method.
In other aspects, the laser ablating may include a first stage and a second stage. The first stage ablates material at a first laser power and the second stage ablates material at a second laser power, the first laser power being different than the second laser power.
In another respect, the invention is a method of coating a substrate with an oriented film. A target including Cp*2Co+ or Cp2Fe is provided. Pulsed laser radiation having an energy between about 70 mJ/pulse and about 200 mJ/pulse at a repetition rate of between about 1 Hz and about 50 Hz is directed to the target to create a plume. The substrate is heated. A pressure between about 150 mTorr and about 350 mTorr about the substrate is maintained. The substrate is vibrated within the plume to coat a film on the substrate, and the film is heated in a synthesis gel of the target to form the oriented film. In another respect, the invention is a coated substrate made by this method.
In other aspects, the method may also include washing or calcining the oriented film.